Luca Alberucci. Strictness of the Modal µ-Calculus Hierarchy. In Erich Grädel, Wolfgang Thomas, Thomas Wilke, editors, Automata, Logics, and Infinite Games: A Guide to Current Research [outcome of a Dagstuhl seminar, February 2001]. Volume 2500 of Lecture Notes in Computer Science, pages 185-201, Springer, 2001. [doi]
Abstract is missing.